Some years ago, Michel-Andre found himself staring at the body of a dead whale on a beach in the Canary Islands. It was obvious that the animal had been struck violently by a ship——but why? Only later, after surveying the whales which lived in the area and measuring the increase of sound pollution from ships did it become clear that there was a link.
The whales had become desensitised to the noise of approaching boats and were being struck by them, often seriously. "We never thought that this could be something that could kill," recalls (回忆) Andre, who is the director of the Laboratory of Applied Bioacoustics at the Technical University of Catalonia, Barcelona.
Andre has spent 20 years developing an advanced system to better understand why incidents like this happen. His underwater microphones have exposed a world of deafening sound and animal communication never observed with such clarity(清晰) before.
It was not an easy task. Sound waves don't travel through water in the uniform, predictable way they do through the air. Instead, the temperature, salinity (盐度) and, flow of water have great effects on their path.
What can be done? One solution is to change shipping routes to courses where ships are statistically less likely to meet animals. It's also possible to slow ships down to 18km/h or less, which is less likely to seriously injure a whale.
As for dealing with the root cause of the problem, the UN's International Maritime Organisation has already published guidelines on how to quieten ships, but it will be a while before the effects of such changes might be observed.
"The ocean is not our world," comments Andre. But it is ours to look after. And thanks to his work, we can better understand the effects of subsea sound pollution.
